The cellular bases for slow waves, oscillatory prepotentials and spikes are being investigated. Slow waves result from an electrogenic sodium pump but the prime pacemaker is being sought in the threshold of either intracellular sodium or ATP production. Electrotonic spread between muscle fibers and muscle layers will be examined. Other types of spontaneous activity in different gastrointestinal muscles from several species are to be measured as a function of ions in the medium. Recording from neurons of myenteric and submucous plexus will elucidate interneuronic interactions, the modulations by the plexuses of myogenic rhythms and the autonomic influences on plexus neurons.